This application is based on patent application Nos. 9-212127, 9-212128, and 9-212129 filed in Japan, the contents of which is hereby incorporated by reference.
This invention relates to an image processing apparatus, particularly to synthesis of a plurality of partial images into a single image bearing the entirety of an object image.
There have been known image sensing apparatuses used in a digital video camera and a digital still camera in which a solid state image pickup device including CCD (Charge Coupled Device) is used. For instance, Japanese Unexamined Patent Publication Nos. 5-137059 and 6-141246 disclose a method in which an object image is partially picked up by each of a plurality of image pickup devices, the partially picked up images are processed to produce a synthesized image representative of the overall object image, thereby improving a resolution of the synthesized image.
Japanese Unexamined Patent Publication No. 3-74991 discloses an image reading apparatus including a plurality of image pickup devices to obtain image data of divided areas of an object, respectively. The pickup areas of the plurality of image pickup devices overlap one another at their respective boundary portions. In this apparatus, to produce a synthesized image, detected is a pixel position which provides data having a small spatial density gap with respect to that of adjacent or nearby pixel, and image data picked up by one image pickup device and image data picked up by another image pickup device are joined one another at the detected pixel position to produce a synthesized image.
In the case where an object image is divided into partial images and picked up by a plurality of image pickup devices, and the picked up partial images are joined one another to produce a synthesized object image, a difference among the sensitivity of image pickup devices is liable to generate a gap in image density at a boundary or a joined portion, and to consequently generate a synthesized image having an undesirable gap.
Japanese Unexamined Patent Publication Nos. 5-137059 and 6-141246 disclose the technology that a plurality of image pickup devices pick up an object image portion by portion. However, these publications are silent on the problem of a gap in image density of a synthesized image at a boundary portion due to the sensitivity difference of the image pickup devices.
Japanese Unexamined Patent Publication No. 3-74991 recites a method for improving an image quality deterioration such as image incongruity. However, in this publication, a position of a less density gap is detected line by line in the boundary portion, and partial images are joined one another considering the detected position per line. Consequently, this method requires a complicated process and takes a long processing time.
Further, the partial images are joined in the direction of line, i.e., horizontal direction. Accordingly, this method is not feasible in effectively suppressing a drastic density gap in a boundary portion in the direction of column, i.e., vertical direction. Also, this method is not effective in reducing the image density gap at the boundary portion due to a sensitivity difference of image pickup devices, and accordingly not feasible in producing a synthesized image with enhanced image congruity.
Japanese Unexamined Patent Publication No. 8-289144 discloses a video scanner in which a first correction data for correcting a difference in the performance characteristic of an image pickup device and a second correction data for correcting a difference in a light amount distribution of a focusing lens for focusing a light image on a sensing surface of the image pickup device are stored in advance to perform a shading correction of an image picked up by the image pickup device using the first correction data and the second correction data.
Japanese Unexamined Patent Publication No. 8-294133 discloses a video camera in which a shading correction is performed using position data of a zooming lens and data on an aperture value of a diaphragm.
Japanese Unexamined Patent Publication No. 8-279902 discloses an image pickup device in which stored is a correction data that is set based on a relationship between an incident angle of a light ray incident upon a sensing surface of an image pickup device via a taking lens and an output level of the image pickup device to perform a shading correction of an image picked up by the image pickup device using the correction data.
The above three publications, i.e., Nos. 8-289144, 8-294133, and 8-279902 disclose the various shading corrections to correct a difference in sensitivity of an image pickup device. In the case where one sensing surface is defined by plural image pickup devices, an additional image processing is required in which partial images respectively sensed by the image pickup devices are joined to produce an image representative of the entirety of an object image. Accordingly, to obtain a synthesized image with a less density gap between the partial images, there should be considered a process of linking an image joining and a shading correction.
However, the shading correction disclosed in the above three publications is applicable merely to a case where a sensing surface is defined by one image pickup device. None of these three publications discloses a process of linking an image joining and a shading correction.
It is an object of the present invention to provide an image processing apparatus which has overcome the problems residing in the prior art.
According to an aspect of the present invention, an image processing apparatus comprises: a partial image data generator which generates a plurality of partial image data pertaining to a plurality of partial images of an object respectively, one partial image being partially overlapped another partial image in a boundary portion; a boundary image data generator which generates boundary image data pertaining to the boundary portion based on image data pertaining to the respective overlapped portions; and an image synthesizer which synthesizes the plurality of partial image data by way of the generated boundary image data to generate image data pertaining to a single image of the object.
According to another aspect of the present invention, an image processing apparatus comprises: a partial image data generator which generates a plurality of partial image data pertaining to a plurality of partial images of an object respectively, one partial image being partially overlapped another partial image in a boundary portion; and an image synthesizer which executes density correction of image data pertaining to the respective overlapped portions, and synthesizes the plurality of corrected partial image data to generate image data pertaining to a single image of the object.
According to still another aspect of the present invention, an image processing apparatus comprises: a plurality of image pickup devices which generate a plurality of partial image data pertaining to a plurality of partial light images of an object respectively, each image pickup device including an arrangement of a number of photoelectric conversion elements respectively attached with three primary color filters in a predetermined positional relationship; an image data interpolator which performs interpolation of partial image data of each primary color generated by each image pickup device; and an image synthesizer which synthesizes the plurality of interpolated partial image data to generate image data pertaining to a single image of the object.
According to yet still another aspect of the present invention, an image processing apparatus comprises: a plurality of image pickup devices which generate a plurality of partial image data pertaining to a plurality of partial light images of an object respectively, each image pickup device including a number of photoelectric conversion elements; a memory which stores correction data for correcting a variation in the photoelectric conversion elements of each image pickup device; an image data corrector which corrects partial image data generated by each image pickup device based on correction data stored in the memory; and an image synthesizer which synthesizes the plurality of corrected partial image data to generate image data pertaining to a single image of the object.